The present invention relates generally to a torsional vibration damping device, and more particularly, to a torsional vibration damping device for use between an input rotation member and an output rotation member of a power transmission apparatus.
Viscous or fluid dampening devices employed in automotive flywheel devices are known. Such dampening devices are typically disposed between an input flywheel and an output flywheel of a flywheel assembly or power transmission apparatus. Examples of this type of conventional device include a flywheel device used in, for example, the engine of an automobile.
One such prior art device in includes a first flywheel, a second flywheel coupled coaxially to the first flywheel for limited rotary displacement, and a viscous damper mechanism disposed between both the flywheels for elastically connecting the flywheels to each other and dampening torsional vibration between the flywheels by the viscous resistance of viscous fluid in response to rotary displacement between the two flywheels. The viscous dampening mechanism has an annular case fixed to the first flywheel and choke activating members disposed so as to be circumferentially movable within the annular case. The annular case is filled with viscous fluid. The dampening mechanism includes an output member connected to the second flywheel, and has a plurality of projections projected into the annular case. The choke activating members are in a cap shape, and are respectively fitted in the projections of the output member and are movable through a predetermined angle relative to the projections. Chokes through which viscous fluid can pass are formed between the choke activating members and the projections.
In the above described conventional torsional vibration damping device, fluid passes through the chokes formed between the choke activating members and the projections of the output member in response to relative displacement of the first and second flywheels. The chokes limit fluid passage thus dampening vibration during relative displacement of the flywheels. In addition, if respective ends of the choke activating members abut against the projections, the chocks are closed.
In the conventional device, however, there is typically insufficient resistance force to restrain the longitudinal vibration of the body of an automobile during tip-in and tip-out of the automobile and the vibration thereof when starting the engine. The reason for this is that the volume of viscous fluid in the annular case is insufficient, thereby to make it difficult to obtain a sufficient resistance force.
In the above described conventional torsional damping device, a radially outer surface of the output member functions as a part of each chokes. Since the radial outer surface of the output member has a plurality of radial projections, it is difficult to manufacture, machine or process the radially outer surface of the output member with high precision.